JPH0552423U - Ball screw device - Google Patents

Abstract

(57) [Summary] [Purpose] A return tube and bridges are not required, enabling downsizing. [Structure] A male screw groove 9 is provided on the outer peripheral surface of the non-rotatable output shaft 2,
Female screw grooves 10 are provided on the inner peripheral surfaces of rotatable nut cylinders 11, respectively. A plurality of balls 8 and 8 are rotatably provided between the screw grooves 9 and 10. The movement of the balls 8, 8 along the female screw groove 10 is caused by the spiral deflectors 16, 1.
Limit by 6. The balls 8, 8 of which movement is blocked by the deflectors 16, 16 are circulated by the pockets 15 on the inner peripheral surface of the nut cylinder 11.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The ball screw device according to the present invention is incorporated into, for example, an electric linear actuator for driving a flow control valve or the like provided in the middle of various hydraulic circuits, and is used to convert the rotational motion of an electric motor into a linear motion. ..

[0002]

[Prior Art]

 For example, in order to drive a flow control valve or the like provided in a hydraulic circuit of an automobile based on a command from a controller, an electric linear actuator is required. For this reason, electric linear actuators that combine a solenoid and a compression spring have been used in the past.

[0003] In this conventionally known electric linear actuator, a displacement member such as a rod is biased to one side by the compression spring, and when it becomes necessary to displace the displacement member, the solenoid is actuated. By energizing, the displacement member is displaced against the elastic force of the compression spring. The displacement amount of the displacement member is adjusted by controlling the amount of electricity supplied to the solenoid and changing the magnitude of the force with which the solenoid attracts the displacement member. That is, the displacing member is displaced to a position where the elastic force of the compression spring and the attractive force of the solenoid balance with each other and stops.

However, in the case of the conventional electric linear actuator using the solenoid as described above, a large current needs to be passed through the solenoid when the displacement member is displaced, so that, for example, in a hydraulic circuit of an automobile. If used for switching, it is not preferable because it causes a burden on the battery.

Further, the displacement amount of the displacement member is adjusted by balancing the elastic force of the compression spring and the suction force of the solenoid. However, since the structure in which the displacement member is biased by the compression spring has a large hysteresis, Even if the same current is applied to the solenoid, the amount of displacement greatly differs depending on whether the displacement member is displaced to one side or the other. Therefore, it is difficult to finely adjust the opening of the flow control valve.

In order to solve such a problem, the present applicant previously filed an application for an electric linear actuator as shown in FIGS. 8 to 9 (Japanese Patent Application No. 3-201142). The electric linear actuator according to the present invention is provided with an output shaft 2 which is freely displaceable in the axial direction (left and right direction in FIG. 8) by an engaging portion 1 as shown in FIG. A concentric cylinder 3 rotatably provided about the output shaft 2 and a torsion coil provided between the cylinder 3 and the casing 4 to apply elastic force in the rotational direction to the cylinder 3. A feed which is provided between the spring 5 and the outer peripheral surface of the output shaft 2 and the inner peripheral surface of the cylinder 3 and displaces the output shaft 2 in the axial direction as the cylinder 3 rotates. The screw portion 6 and an electric motor 7 which is provided inside the casing 4 and rotates the cylinder 3 against the elastic force of the torsion coil spring 5 upon energization.

In the case of the electric linear actuator according to the prior invention configured as described above, when the electric motor 7 is not energized, the cylinder 3 is rotated in one direction by the elastic force of the torsion coil spring 5, and this rotation is performed. Accordingly, the output screw 2 is displaced to one end in the axial direction by the feed screw portion 6.

When the electric motor 7 is energized, the cylinder 3 is rotated to a state in which the rotational torque of the electric motor 7 determined according to the amount of energization and the elastic force of the torsion coil spring 5 are in equilibrium. Stop as it is. Then, with the rotation of the cylinder 3, the output screw 2 is displaced by the feed screw portion 6 toward the other end in the axial direction.

[0009]

[Problems to be solved by the device]

 The electric linear actuator according to the previous invention configured as described above has solved the problems of the conventional electric linear actuator using the above-mentioned solenoid, but still has the following problems to be solved. Have a point.

That is, the feed screw portion 6 for displacing the output shaft 2 in the axial direction along with the rotation of the cylinder 3 is configured to include a plurality of balls 8 and 8 and 8 is movable along an external thread groove 9 having an arcuate cross section formed on the outer peripheral surface of the output shaft 2 and a female thread groove 10 having an arcuate cross section formed on the inner peripheral surface of the cylinder 3. Therefore, a return tube is required to return the balls 8, 8 which have moved to one end of the screw grooves 9, 10 to the other end of the screw grooves 9, 10. For this reason, it is inevitable that the feed screw portion 6 becomes complicated and large, and it becomes difficult to design an electric linear actuator to be installed in a narrow portion.

Also, instead of the return tube, there is known a structure in which a piece provided with a passage for returning the balls 8 and 8 is attached to an elongated hole formed in the cylinder 3, but the return tube is also provided. Has the same problem as the case of providing.

The ball screw device of the present invention eliminates the above-mentioned inconvenience.

[0013]

[Means for Solving the Problems]

 The ball screw device of the present invention includes a shaft having a cylindrical outer peripheral surface, a male screw groove formed on the outer peripheral surface of the shaft, a periphery of the shaft, a shaft concentric with the shaft, and a pair relative to the shaft. A nut cylinder having a cylindrical inner peripheral surface supported so as to be freely rotatable, a female screw groove formed in the inner peripheral surface of the nut cylinder in the same phase as the male screw groove, and the female screw groove. And a plurality of balls provided between the male screw groove and the male screw groove, and formed in a spiral coil shape, on one peripheral surface of the outer peripheral surface of the shaft and the inner peripheral surface of the nut cylinder, on the peripheral surface. A pair of deflectors fixed in a state of being fitted to both ends of the formed one screw groove and a discontinuous portion of the pair of deflectors are formed on the one peripheral surface, and And a pocket for communicating different phase portions of one screw groove.

Then, the ball rolling along the one screw groove based on the relative rotation between the shaft and the nut cylinder is moved by the inner end portion of one of the pair of deflectors, It functions like sending it to the pocket.

[0015]

[Action]

 In the case of the ball screw device of the present invention configured as described above, as one member of the shaft and the nut cylinder is rotated, the other member is displaced in the axial direction.

As described above, in the case of converting the rotational movement of one member into the displacement of the other member in the axial direction, in the ball screw device of the present invention, a plurality of balls roll and the male screw It moves along the groove and the female screw groove and is fed into the pocket by the inner end of one of the pair of deflectors. The ball sent into the pocket is sent to different phase portions of the screw groove along the pocket, and while rolling again, moves along the male screw groove and the female screw groove.

Therefore, a return tube or piece for returning the ball to the original is not required, and the ball screw device can be downsized.

[0018]

【Example】

 1 to 4 show a first embodiment of the present invention. The output shaft 2 having a cylindrical outer peripheral surface can be displaced only in the axial direction (left and right direction in FIGS. 1 and 2) by the engaging portion as shown in FIG. A male screw groove 9 having an arc-shaped cross section is formed on the outer peripheral surface of the output shaft 2.

On the other hand, a cylindrical nut cylinder 11 is rotatably supported around the output shaft 2 concentrically with the output shaft 2. The nut cylinder 11 is formed by combining a nut cylinder body 12 and a cover cylinder 13 as shown in FIG. 3, in which the female thread groove 10 having an arc-shaped cross section is formed on the inner peripheral surface of the nut cylinder body 12. It is formed in the same phase as the male screw groove 9.

Further, a long hole 14 is formed in an intermediate portion of the nut cylinder body 12 so as to be inclined in a direction opposite to that of the female screw groove 10. Both ends of the elongated hole 14 reach different phase portions of the female screw groove 10, that is, a part of the female screw groove 10 and two axially separated position portions. On the other hand, the cover cylinder 13 has an inner diameter that is the same as the outer diameter of the nut cylinder main body 12 or slightly smaller than this outer diameter in the free state. As shown in FIGS. 1 and 2, such a cover cylinder 13 is externally fitted and fixed to the nut cylinder body 12 to close the outer peripheral side opening of the elongated hole 14.

In the state where the nut cylinder body 12 and the cover cylinder 13 are combined in this way, the elongated hole 14 is provided between the male screw groove 9 and the female screw groove 10 as described below. A pocket 15 is formed for returning the balls 8, 8 sent in one direction between the screw grooves 9, 10 to their original positions. Therefore, the nut cylinder body 12 has a thickness dimension larger than the outer diameter dimension of each of the balls 8, 8.

A plurality of balls 8 are rotatably provided between the male screw groove 9 and the female screw groove 10 so that when the nut cylinder 11 rotates, the output shaft 2 moves in the axial direction. It is designed to be displaced.

Further, deflectors 16, 16 as shown in FIG. 4 are fitted and fixed in the female screw groove 10 formed on the inner peripheral surface of the nut cylinder 11. Each of the deflectors 16 and 16 is formed in the shape of a compression coil spring having the same pitch as that of each of the screw grooves 9 and 10, and is internally fitted and fixed to both ends of the female screw groove 10. In this state, the deflectors 16 and 16 are not fitted between the inner end portions of the deflectors 16 and 16 at the intermediate portion of the female screw groove 10 and the plurality of balls 8 and 8 are not fitted. There is a guide part 17 that can move freely. Both ends of the pocket 15 are aligned with both ends of the guide portion 17.

An inclined surface 18 is formed at an inner end portion of each of the deflectors 16 and 16, and the plurality of balls 8 and 8 are present at an intermediate portion of the female screw groove 10 based on rotation of the nut cylinder 11. When rolling along the guiding portion 17, the balls 8, 8 fed to the end portion of the guiding portion 17 are fed into the pocket 15 by the inclined surface 18.

In the case of the ball screw device of the present invention configured as described above, when the nut cylinder 11 is rotated by an electric motor or the like, the output shaft 2 is displaced in the axial direction. That is, when the nut cylinder 11 is rotated, the plurality of balls 8, 8 move along the female screw groove 10 on the inner peripheral surface of the nut cylinder 11 while rotating on their own axis. At this time, since the output shaft 2 does not rotate, the balls 8, 8 press the side surface of the male screw groove 9 formed on the outer peripheral surface of the output shaft 2 to displace the output shaft 2 in the axial direction. ..

As described above, when converting the rotational movement of the nut cylinder 11 into the linear movement of the output shaft 2, the balls 8, 8 are fed in one direction through the guide portion 17 at the intermediate portion of the female screw groove 10. , Reaches to one end of the guide portion 17. Since both ends of the guide portion 17 are partitioned by the inner end portions of the pair of deflectors 16 and 16, the balls 8 and 8 that reach the end portion of the guide portion 17 are not separated by either deflector 16. It is guided by the inclined surface 18 formed at the inner end portion and fed into the pocket 15 provided on the inner peripheral surface of the nut cylinder 11.

Since the balls 8, 8 are fed into the pocket 15 by the inclined surface 18 continuously as long as the nut cylinder 11 is rotating, the balls 8, 8 fed into the pocket 15 are It is pushed by the balls 8, 8 fed later, is fed to different phase portions of the female screw groove 10 along the pocket 15, and is rolled again along the male screw groove 9 and the female screw groove 10. Moving.

Therefore, a return tube or piece for returning the balls 8 to the original is not required, and the ball screw device can be downsized. The cross-sectional shape of the male screw groove 9 and the female screw groove 10 is not limited to the arc shape, but may be a Gothic arch shape or a V shape.

Next, FIGS. 5 to 6 show a second embodiment of the present invention. In the first embodiment described above, the pair of deflectors 16 and 16 are internally fitted and fixed to both ends of the female screw groove 10, and the pocket 15 is formed on the inner peripheral surface of the nut cylinder 11. In the case of the present embodiment, the pair of deflectors 16 and 16 are externally fitted and fixed to both ends of the male screw groove 9, and the outer peripheral surface of the output shaft 2 is recessed to form the pocket 19. ing. Other configurations and actions are similar to those of the above-described first embodiment.

In the first and second embodiments, the deflector 16 and the pocket 15 are attached to the shaft for the purpose of improving the load capacity and preventing the tilt between the nut cylinder 11 and the output shaft 2. It can also be installed at multiple points in the direction.

Next, FIG. 7 shows a state where the ball screw device of the present invention is incorporated in an electric linear actuator. The output shaft 2 provided in the central portion is displaced only in the axial direction (the left-right direction in FIG. 7) without rotating due to the engagement with the connecting rod 20, and drives the valve body of the flow control valve ( Translate it). A cylinder 21 is provided around the output shaft 2 concentrically with the output shaft 2, and a casing 22 is provided around the cylinder 21. The cylinder 21 is rotatably supported inside the casing 22 via rolling bearings 23, 23.

A male screw groove 9 is formed on a portion of the outer peripheral surface of the output shaft 2 which is located inside the cylinder 21, and the inner peripheral surface of the cylinder 21 is opposed to the male screw groove 9. The nut cylinder 11 is fixed to the. The nut cylinder 11 and the output shaft 2 compose a ball screw device of the present invention, and the output shaft 2 is axially displaced along with the rotation of the cylinder 21.

Further, inside the casing 22, an electric motor 24 of, for example, a stepping servo type is provided in order to rotate the cylinder 21 with energization. That is, the permanent magnet 25 is fixed to the outer peripheral surface of the cylinder 21, and the outer peripheral surface of the permanent magnet 25 is opposed to the inner peripheral surface of the stator 26 provided inside the casing 22 which also serves as the stator iron core. ing. By energizing the stator 26, the permanent magnet 25 can be driven to rotate in a desired direction by a desired angle.

In the electric linear actuator incorporating the ball screw device of the present invention constructed as described above, when the output shaft 2 is displaced, the stator 26 constituting the electric motor 24 is energized. Along with the energization of the stator 26, the cylinder 21 fixed with the permanent magnet 25 facing the stator 26 rotates, and the output shaft 2 is displaced along the axial direction as the cylinder 21 rotates. ..

[0035]

[Effect of the device]

 Since the ball screw device of the present invention is constructed and operates as described above, a return tube and a piece for circulating the balls forming the feed screw portion are unnecessary, and the ball screw device can be installed in a narrow portion due to miniaturization. Easier to design electric linear actuators.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part showing a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a side view showing the nut cylinder in a state in which the cover cylinder is cut.

FIG. 4 is an enlarged side view of the deflector.

FIG. 5 is a sectional view showing a main part of a second embodiment of the present invention.

6 is a sectional view taken along line BB of FIG.

FIG. 7 is a half sectional view of an electric linear actuator incorporating the ball screw device of the present invention.

FIG. 8 is a cross-sectional view showing an electric linear actuator of the prior invention.

9 is an enlarged sectional view taken along line CC of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engagement part 2 Output shaft 3 Cylindrical 4 Casing 5 Torsion coil spring 6 Feed screw part 7 Electric motor 8 Ball 9 Male screw groove 10 Female screw groove 11 Nut cylinder 12 Nut cylinder body 13 Cover cylinder 14 Long hole 15 Pocket 16 Deflector 17 Guide part 18 Inclined surface 19 Pocket 20 Connecting rod 21 Cylindrical 22 Casing 23 Rolling bearing 24 Electric motor 25 Permanent magnet 26 Stator

Claims (1)

[Scope of utility model registration request] 1. A shaft having a cylindrical outer peripheral surface, a male screw groove formed on the outer peripheral surface of the shaft, and a shaft capable of rotating around the shaft concentrically with the shaft and relative to the shaft. A supported nut cylinder having a cylindrical inner peripheral surface, a female screw groove formed on the inner peripheral surface of the nut cylinder in the same phase as the male screw groove, the female screw groove and the male screw groove. A plurality of balls provided between the outer peripheral surface of the shaft and the inner peripheral surface of the nut cylinder on one peripheral surface,
A pair of deflectors fixed in a state of being fitted to both ends of one screw groove formed on the peripheral surface and a discontinuous portion of the pair of deflectors are formed on the one peripheral surface. And a pocket that communicates different phase portions of the one screw groove with each other, the pair of balls rolling along the one screw groove based on relative rotation of the shaft and the nut cylinder. Ball screw device for feeding into the pocket by the inner end of one of the deflectors.